As well as spontaneous human combustion, the second issue of beloved eighties parteork The Unexplained introduces a topic that its readers might have found a little unexpected. For the first time, the magazine was delving into a topic that exists well within the boundaries of accepted science: black holes.
In his article “Black Holes: Where Time Stops, Space Collapses”, astronomer Nigel Henbest delivers a popular introduction to the subject:
A black hole is quite literally a hole in the fabric of space, torn from our Universe by a star collapsing in on itself. It is a region into which matter has fallen and from which nothing, not even light itself, can escape. Within the black hole, there is no up or down; no left or right. Time and space have changed roles with one another.
Just as we on Earth cannot help by travel forward in time, so any space traveller unfortunate enough to fall into a black hole would be sucked into the centre by an infinite density and crushed out if existence. Around the black hole itself is left a gaping hole, a few miles across, where space does not exist. Here, the pull of gravity is stronger than anywhere else in the Universe. Nothing can ever escape from it.
Henbest opens his history of the black hole as a concept with the theory propounded by Pierre-Simon de Laplace in the late eighteenth century that some stars might be so dense that their gravity prevents light from escaping, rendering them invisible. In the twentieth century came Albert Einstein, whose theory of general relativity predicted that black holes could be formed by warps in space – a notion subsequently developed by Karl Schwarzschild, J. Robert Oppenheimer and H. Snyder.
Moving on to research of the sixties and seventies, the article gives potted summaries of theories postulated by Roy Kerr, Roger Penrose and Stephen Hawking. The next topic is the life-cycle of a star, from nebula-fragment, through to red giant, then white dwarf, then neutron star. This provides context for a quick look at means of identifying black holes in space, concluding with two paragraphs on Cygnus X-1.
So far, The Unexplained’s coverage of black holes is decidedly un-sensationalised. It’s the sort of thing you can find in any number of respectable resources on astronomy, and contrasts sharply with the magazine’s usual choice of topic – bigfoot, flying saucers and so forth. But then things change a little…
The second instalment of the series, “Doorway to Beyond: Inside a Black Hole” ran in issue 3. As its title suggests, this piece imagines what might happen should an astronaut enter a black hole.
Henbest opens with the hypothetical scenario of a spaceman “approaching a simple, static, black hole of the type described by Karl Schwarzschild in 1916”, outlining how time runs differently the astronaut as falls closer to the event horizon, so that what seem like mere seconds to him constitutes an infinity for an observer, until he is eventually crushed to infinite density. The article then admits that Schwarzschild’s theories are outdated, and the idea of a static black hole has been largely rejected.
Next, using diagrams provided by Roger Penrose, the article discusses the logistics of flying through a black hole and hypothetically reaching another universe on the other side.
The general thrust is that such a thing would be impossible without either hitting the black hole’s singularity and being destroyed, or by moving faster than light in violation of Einstein’s theories. The exception, Henbest argues, is if the black hole is electrically-charged:
Within an electrically-charged black hole, there is a second ‘inner’ event horizon, lying inside the ‘outer’ horizon which seals the hole from the rest of the Universe. Here space and time change roles again. So although an astronaut falling through the outer event horizon must pursue a one way path inwards, this now takes him only as fa as the inner event horizon. And once inside the inner horizon, out astronaut can manoeuvre how he likes, although he cannot know where he will end up. According to simple calculations, he may re-emerge in another universe, or at the same instant, elsewhere in this Universe.
Still more diagrams illustrate this concept, and Henbest speculates on what might be at the other end of a black hole: “an astronaut… might find himself not only in a universe that was different from our own, but one where gravity, for example, instead of being a force that attracts two objects, is a force that repels. He might find himself, that is, in a ‘negative universe’.”
After describing yet another thing that could go wrong in black hole travel – namely, an astronaut being stretched to breaking point, the end closest to the hole being pulled in faster than the end furthest away – the article posits that this may be avoided if the black hole is sufficiently large, as the black holes thought to exist at the centres of galaxies would be: “massive black holes probably do exist and, in theory at least, could be used as gateways to other universes.”
So, what might happen to the astronaut who makes it through a black hole? Well, the article suggests that he’d come out of a white hole on the other end: “If white holes exist, they are ‘cosmic gushers’, spewing matter and light out in a seemingly inexhaustible fountain.” In the process, the astronaut might have found themselves in another universe or a different time: far in the future, or even back in the past.
Of course, there are rather a lot of “ifs” in all this. The idea of other universes or time travel into the past are themselves entirely hypothetical, so a means of reaching them through black holes is itsel a hypothesis about a hypothesis. Henbest himself acknowledges this: “scientists are now distinctly dubious about universe-hopping through black/white hole tunnels.”
Some of the article’s ideas would later be explored in Kip Thorne’s 1994 book Black Holes and Time Warps. Meanwhile, starting in its fifth issue The Unexplained would begin another series on black holes, this time by Adrian Berry. I’ll be coming to that later.